In a manufacturing system, in order to deliver the finished goods, a lot of elements have to be moved on the production floor from time to time as they are required in different locations. Most of these movements require a manual intervention, although some of them may be automated using robots, conveyors or some other means. Along with these movements, the necessary information needs to follow. In most occasions, this information follows manually, although there exists some ways to partly automate this aspect that will be discussed hereinbelow. Here are examples of movements that can occur in a manufacturing system and the related data that needs to follow these movements;                Machine set-up. In order to prepare a given machine to produce a given part, it needs to be set up with the right tooling, the right recipe or program and the right raw material. All these elements will have to be prepared and, if an error occurs and a wrong element is used or the wrong information about it is entered, the outgoing production will not conform to the specifications. Typically, this set-up is done manually.        Routing of parts. Parts being produced will need to be routed to different stations or machines in a given sequence. This sequence or the stations to be seen may be altered as different quality controls are passed or failed. This routing information needs to follow the goods being produced through the whole manufacturing system and is typically described on sheets of paper or, in the more advanced manufacturing facilities, it can be accessed on a host computer through terminals in strategic places on the manufacturing floor. A lot number generally needs to be entered in the computer in order to know the next process step to be seen and data is entered at each process step.        Physical inventory of raw material and work in progress (WIP). As the raw material is used in the manufacturing system, some may be left over and will await the next production lot that requires this given raw material. Also, as the goods are being produced, they will be moved from station to station in the manufacturing system. Both the raw material and the WIP will need to be tracked for inventory purposes and their physical location will be required to physically find these parts. Generally, this information is gathered manually and, in the best cases, entered in a computer software. This yields an inventory that relies highly on human interventions and that is always outdated as it is not in real-time.        Process control. In order to control the process and the quality of the manufactured products, some process and product information is gathered. This information needs to follow the product and feedback to the process control in order to adjust it.        Similarly, different types of information need to follow the production lots. In its simplest form, this data will be an identifier that will enable to trace back the information on the manufactured goods.        
Automatic Identification Technology
In order to ease the burden for the operator and to reduce the risk of human errors, there exist a number of Automatic Identification (Auto ID) techniques that are used. These systems, such as barcode, Radio Frequency Identification (RFID) and Optical Character Recognition (OCR), are often used to provide a simple identification of an object and their primary benefit in this case is to reduce the time and possible errors associated with the manual entry of this information.
Barcode Technology
One general drawback of using barcodes is the need of a sufficiently large flat area to apply a barcode label which is not always available on raw material, its container, or other parts to be traced. Also, all barcode readers require direct line-of-sight with the barcode label. This can be a major restriction toward complete automation of the reading operation. Finally, barcodes offer a limited number of information that can be written only once (at the printing operation of the barcode) and thus that cannot be altered.
RFID Technology
In addition to barcode labels, which have now become fairly common on many standard materials and containers, some manufacturing systems take advantage of the greater capabilities associated with the use of Radio Frequency Identification (RFID) technology. A typical RFID system is always made up of two components: the transponder, which is located on the object to be identified, and the interrogator or reader, which, depending upon design and the technology used, may be a read or write/read device (herein—in accordance with common usage—the data capture device is always referred to as the reader, regardless of whether it can only read data or is also capable of writing).
The RFID technology offers multiple benefits when compared to other alternatives such as barcodes. Some of the key benefits from the perspective of factory automation include the greater flexibility in packaging, greater and more flexible read-range, larger data storage capability.
Another very significant benefit of RFID technology is related to the read, write and alter capability (as opposed to read only). In addition to recording the identity of the object, it is also possible to track its current state (e.g. processing level, quality data), its past state and its future state (desired end state).
There are two possible methods of controlling a system based upon object data: central and de-central control. In the first method, all elements of the system must be connected, through a network or other means, with a common database in a central computer. In this case, a unique identification number can be stored on a RFID transponder to access all of the relevant data stored in the database. In the second method, the use of readable and writable data carriers opens up the possibility of controlling a system locally, i.e. completely independently of the central process computer. Material and data flow become interlinked. In a manufacturing environment, this is significant since it may be impractical to have all machines and manufacturing systems connected to a single network and central database. This is especially true when a manufacturing process is made up of multiple production steps which may be performed in separate autonomous plants.
Use of Auto ID in a Manufacturing System
The automatic identification techniques are sometimes used in manufacturing environments in order to automate the data acquisition process. The barcode technology is widely used, especially in inventory tracking systems. RFID technology, as it is a newer technology, is not as widely spread. The automotive industry is the sector that is using the most this technology. RFID technology can be found in the following manufacturing applications:                Inventory. Due to the higher cost of the RFID tags compared to barcode labels, this application uses mostly barcodes. This application is very well documented and some companies are working on producing tags that are cheap enough to enable it.        Physical inventory of released material and WIP. This application, although not very common in the industry, is well described in the literature. An example of implementation of such an application can be found at the GM factory in Flint (Mich., U.S.A.) where all engines can be traced in the factory using RFID tags.        Machine set-up and tooling verification. There exist some applications in the industry that address these problems. For example, in the woodworking industry, some German companies equipped the drill bits of their CNC milling machines with RFID technology. The milling machine's program is selected by the operator. The milling machines have integrated readers that are solely used to make sure the milling machine is using the right tool for the milling program that was selected. Another example, in the automotive industry, is the use of this technology in the assembly operations. The car bodies, instead of being identified manually, are fitted with an RFID transponder that has all the body information (BMW's factory in Dingolfing, Germany). This information appears on a screen and is read at each station by the operator to set up each specific station. The collected information is not carried through the stations.        Routing of the WIP. As the goods being produced need to be routed from station to station or from machine to machine, the RFID technology can offer a mean to automate the routing decisions and make sure that all parts go through the right process steps in the right order. This application, although not widely spread in the industry yet, is well described in the literature. One example of such application can be found in the meat industry, where the company J.M. Schneider Meats uses the RFID technology to ensure that the meat sees the right processes in the right order. It also uses the technology to identify and track (WIP tracking) the meat through the process.        
Although the above described monitoring systems are useful, they are only adapted to perform a single task. There is a need for a new control and monitoring system that can handle different applications during a manufacturing process.